The thing most people miss about Singapore: no law forces a company to pay retrenchment benefits.
The legal position
Singapore has no statutory requirement for severance pay. Retrenchment benefits are a matter of contractual agreement or company policy, not law.
Under the Employment Act, an employee with at least two years of continuous service is eligible for retrenchment benefits if specified in their employment contract or collective agreement.
If no such provision exists, the employer is not legally obligated to pay.
Your contract is the first place to look
The terms of your employment contract are binding on both parties. That should be your first recourse, followed by company internal policies.
The market norm
MOM's Tripartite Advisory on Managing Excess Manpower sets a norm of two weeks to one month of salary for each year of service.
Unionised firms usually pay a full month per year.
The Advisory recommends providing retrenchment benefits but does not mandate them.